/*
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 Copyright(c) 2005 Adobe Systems Incorporated. All rights reserved.

 Please read this Source Code License Agreement carefully before using
 the source code.

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 */

package com.adobe.crypto {
import com.adobe.utils.IntUtil;

import flash.utils.ByteArray;

import mx.utils.Base64Encoder;

/**
 * The SHA-256 algorithm
 *
 * @see http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf
 */
public class SHA256 {

    /**
     *  Performs the SHA256 hash algorithm on a string.
     *
     *  @param s        The string to hash
     *  @return            A string containing the hash value of s
     *  @langversion    ActionScript 3.0
     *  @playerversion    9.0
     *  @tiptext
     */
    public static function hash(s:String):String {
        var blocks:Array = createBlocksFromString(s);
        var byteArray:ByteArray = hashBlocks(blocks);

        return IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true);
    }

    /**
     *  Performs the SHA256 hash algorithm on a ByteArray.
     *
     *  @param data        The ByteArray data to hash
     *  @return            A string containing the hash value of data
     *  @langversion    ActionScript 3.0
     *  @playerversion    9.0
     */
    public static function hashBytes(data:ByteArray):String {
        var blocks:Array = createBlocksFromByteArray(data);
        var byteArray:ByteArray = hashBlocks(blocks);

        return IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true)
                + IntUtil.toHex(byteArray.readInt(), true);
    }

    /**
     *  Performs the SHA256 hash algorithm on a string, then does
     *  Base64 encoding on the result.
     *
     *  @param s        The string to hash
     *  @return            The base64 encoded hash value of s
     *  @langversion    ActionScript 3.0
     *  @playerversion    9.0
     *  @tiptext
     */
    public static function hashToBase64(s:String):String {
        var blocks:Array = createBlocksFromString(s);
        var byteArray:ByteArray = hashBlocks(blocks);

        // ByteArray.toString() returns the contents as a UTF-8 string,
        // which we can't use because certain byte sequences might trigger
        // a UTF-8 conversion.  Instead, we convert the bytes to characters
        // one by one.
        var charsInByteArray:String = "";
        byteArray.position = 0;
        for (var j:int = 0; j < byteArray.length; j++) {
            var byte:uint = byteArray.readUnsignedByte();
            charsInByteArray += String.fromCharCode(byte);
        }

        var encoder:Base64Encoder = new Base64Encoder();
        encoder.encode(charsInByteArray);
        return encoder.flush();
    }

    private static function hashBlocks(blocks:Array):ByteArray {
        var h0:int = 0x6a09e667;
        var h1:int = 0xbb67ae85;
        var h2:int = 0x3c6ef372;
        var h3:int = 0xa54ff53a;
        var h4:int = 0x510e527f;
        var h5:int = 0x9b05688c;
        var h6:int = 0x1f83d9ab;
        var h7:int = 0x5be0cd19;

        var k:Array = new Array(0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2);

        var len:int = blocks.length;
        var w:Array = new Array(64);

        // loop over all of the blocks
        for (var i:int = 0; i < len; i += 16) {

            var a:int = h0;
            var b:int = h1;
            var c:int = h2;
            var d:int = h3;
            var e:int = h4;
            var f:int = h5;
            var g:int = h6;
            var h:int = h7;

            for (var t:int = 0; t < 64; t++) {

                if (t < 16) {
                    w[t] = blocks[ i + t ];
                    if (isNaN(w[t])) {
                        w[t] = 0;
                    }
                } else {
                    var ws0:int = IntUtil.ror(w[t - 15], 7) ^ IntUtil.ror(w[t - 15], 18) ^ (w[t - 15] >>> 3);
                    var ws1:int = IntUtil.ror(w[t - 2], 17) ^ IntUtil.ror(w[t - 2], 19) ^ (w[t - 2] >>> 10);
                    w[t] = w[t - 16] + ws0 + w[t - 7] + ws1;
                }

                var s0:int = IntUtil.ror(a, 2) ^ IntUtil.ror(a, 13) ^ IntUtil.ror(a, 22);
                var maj:int = (a & b) ^ (a & c) ^ (b & c);
                var t2:int = s0 + maj;
                var s1:int = IntUtil.ror(e, 6) ^ IntUtil.ror(e, 11) ^ IntUtil.ror(e, 25);
                var ch:int = (e & f) ^ ((~e) & g);
                var t1:int = h + s1 + ch + k[t] + w[t];

                h = g;
                g = f;
                f = e;
                e = d + t1;
                d = c;
                c = b;
                b = a;
                a = t1 + t2;
            }

            //Add this chunk's hash to result so far:
            h0 += a;
            h1 += b;
            h2 += c;
            h3 += d;
            h4 += e;
            h5 += f;
            h6 += g;
            h7 += h;
        }

        var byteArray:ByteArray = new ByteArray();
        byteArray.writeInt(h0);
        byteArray.writeInt(h1);
        byteArray.writeInt(h2);
        byteArray.writeInt(h3);
        byteArray.writeInt(h4);
        byteArray.writeInt(h5);
        byteArray.writeInt(h6);
        byteArray.writeInt(h7);
        byteArray.position = 0;
        return byteArray;
    }

    /**
     *  Converts a ByteArray to a sequence of 16-word blocks
     *  that we'll do the processing on.  Appends padding
     *  and length in the process.
     *
     *  @param data        The data to split into blocks
     *  @return            An array containing the blocks into which data was split
     */
    private static function createBlocksFromByteArray(data:ByteArray):Array {
        var oldPosition:int = data.position;
        data.position = 0;

        var blocks:Array = new Array();
        var len:int = data.length * 8;
        var mask:int = 0xFF; // ignore hi byte of characters > 0xFF
        for (var i:int = 0; i < len; i += 8) {
            blocks[ i >> 5 ] |= ( data.readByte() & mask ) << ( 24 - i % 32 );
        }

        // append padding and length
        blocks[ len >> 5 ] |= 0x80 << ( 24 - len % 32 );
        blocks[ ( ( ( len + 64 ) >> 9 ) << 4 ) + 15 ] = len;

        data.position = oldPosition;

        return blocks;
    }

    /**
     *  Converts a string to a sequence of 16-word blocks
     *  that we'll do the processing on.  Appends padding
     *  and length in the process.
     *
     *  @param s    The string to split into blocks
     *  @return        An array containing the blocks that s was split into.
     */
    private static function createBlocksFromString(s:String):Array {
        var blocks:Array = new Array();
        var len:int = s.length * 8;
        var mask:int = 0xFF; // ignore hi byte of characters > 0xFF
        for (var i:int = 0; i < len; i += 8) {
            blocks[ i >> 5 ] |= ( s.charCodeAt(i / 8) & mask ) << ( 24 - i % 32 );
        }

        // append padding and length
        blocks[ len >> 5 ] |= 0x80 << ( 24 - len % 32 );
        blocks[ ( ( ( len + 64 ) >> 9 ) << 4 ) + 15 ] = len;
        return blocks;
    }
}
}